It's long been assumed that Apple would eventually add a cellular modem to completely free the Apple Watch from an iPhone and make the watch a truly independent device. But is that really necessary? The short answer: no. The longer answer: maybe … in some very specific cases.

"A watch does not replace your smartphone," said Avi Greengart, research director of consumer platforms and devices with market-research firm GlobalData. "There are some situations where having a smartphone in your pocket is inconvenient and having access to key information would be helpful, like if you're swimming or running or working out in the gym. Those are the use cases where I could see Apple having a connected smartwatch would be improvement. It wouldn't be an improvement for everybody."

Apple is already targeting fitness enthusiasts with the waterproof Apple Watch Series 2, which comes with GPS for running and swim-specific workout tracking. The Series 2 even comes in a Nike flavor with breathable, perforated sport bands and customized watch faces. The cellular model would be another way to appeal to people who prefer to work out unencumbered by smartphones, which seem to be growing ever larger each year.

"When I go for a run, I don't want this bulky phone attached to me," said indie-app developer Brian Mueller, who designed the popular Carrot Weather app for iOS, macOS and watchOS. "I think it would be great to get notifications that it was going to start raining in 10 minutes while I'm running. I'm really excited to roll that functionality out to my users."

An LTE Apple Watch would require a separate monthly data plan, which is a barrier to buy-in, Greengart said. But being able to track workouts, receive text messages, make phone calls, download songs, get weather alerts and even use Apple Pay to buy stuff, all without carrying an iPhone in your pocket, could prove compelling for many current and would-be Apple Watch users.

Several Redditors have said that the combination of Apple's Bluetooth AirPods and the Apple Watch, which connect seamlessly and let you listen to music or take phone calls directly from the watch, is ideal for replacing an iPhone when you're on the go.

Of course, the Apple Watch wouldn't be the first smartwatch with cellular connectivity. Can it succeed where others, like the Samsung Gear S3 and LG's Watch Urbane, have struggled to find an audience?

Apple will have to make a convincing case for why you need a data plan for your wrist.

"I don't think any vendor who has put a cellular radio in a smartwatch has done a good job of that," Greengart said. "They've said, 'Now you've got a Dick Tracy watch on your wrist, and it's cool.' But the cool only goes as far as the concept. The smartwatches we've seen with cellular radios go from size XL to boat anchor."

The Gear S3 is a whopping 46 millimeters in diameter, while the second-gen LG Watch Urbane is slightly less massive, at 44.5mm. The largest Apple Watch is 42mm, but it also comes in a smaller, 38mm version.

Apple would have to continue to offer smaller sizing to appeal to more people, Greengart said.

A waterproof smartwatch with GPS and LTE that's small enough to fit on nearly everyone's wrist without sacrificing battery life seems like a tall order. Has Apple finally figured it out? We may find out as soon as September. Bloomberg reported that Apple is aiming to launch the new watch model when the company takes the wraps off the iPhone 8 this fall.